Environmental Reporting, Ministry for the Environment and Statistics New Zealand
Position Name
Analyst
Contact Info
Contact
Address
Address
Delivery Point
23 Kate Sheppard Place, PO Box 10362
City
Wellington 6143
Country
New Zealand
Electronic Mail Address
Environmental.Reporting@mfe.govt.nz
Role
Role Code
distributor
Date Stamp
Date
2016-02-18
Metadata Standard Name
ANZLIC Metadata Profile: An Australian/New Zealand Profile of AS/NZS ISO 19115:2005, Geographic information - Metadata
Metadata Standard Version
1.1
Reference System Info
Reference System
Reference System Identifier
Identifier
Code
2193
Identification Info
Data Identification
Citation
Citation
Title
Lake water quality, 2009–13
Date
Abstract
"The Lake Trophic Level Index (TLI) characterises the life supporting capacity of a lake based on nutrient enrichment. In general, the higher the TLI score, the poorer the water quality in the lake. Lakes with extremely poor quality are rarely suitable for recreation and provide poor quality habitat for aquatic species. Care should be taken when interpreting these results. Monitored lakes consist of about 4 percent of all New Zealand lakes, and programmes may focus on those that have poor water quality or are at risk due to the type of land use in their catchment. After checking for data consistency, the lakes considered suitable for national comparison are sparsely and unevenly distributed, with gaps in the Manawatu, Taranaki, Tasman, Marlborough, Otago, and West Coast regions. The lakes considered in the analysis are located mainly in Northland, Bay of Plenty, Hawke’s Bay, and Canterbury. This dataset relates to the ""Lake water quality: trophic level index"" measure on the Environmental Indicators, Te taiao Aotearoa website. "
Status
Progress Code
completed
Point Of Contact
Responsible Party
Organisation Name
Environmental Reporting, Ministry for the Environment and Statistics New Zealand
Source: National Institute of Water and Atmospheric Research
Method: "The Trophic Level Index (TLI) has been calculated using three separate water quality measurements – total nitrogen, total phosphorus, and chlorophyll–a. Total nitrogen and total phosphorus are nutrients. Large amounts encourage the growth of algae and weed species which can lead to poor water quality. Chlorophyll–a is the green colour in plants and its measurement indicates how much algae the lake has. TLI scores less than three indicate low levels of nutrients and algae which is characteristic of clear or blue lakes. TLI scores greater than four indicate eutrophic conditions with high amounts of nutrients and algae. Large shallows may naturally score higher. There are also other important characteristics of lake condition such as the types of fish and aquatic plants present which are not described by the TLI.
The TLI is used to place lakes into nutrient–enrichment categories, known as trophic states (Burns et al, 2000):
- Microtrophic (TLI < 2) lakes are very clean, and often have snow or glacial sources (eg Lake Pukaki in Canterbury).
- Oligotrophic (TLI 2–3) lakes are clear and blue, with low levels of nutrients and algae (eg, Lake Rotoma in the Bay of Plenty).
- Mesotrophic (TLI 3–4) lakes have moderate levels of nutrients and algae (eg, Lake Rerewhakaaitu in the Bay of Plenty).
- Eutrophic ( TLI 4–5) lakes are green and murky, with higher amounts of nutrients and algae (eg, Lake Rotoroa in Northland).
- Supertrophic or Hypertrophic (TLI > 5) lakes have extremely high levels of phosphorus and nitrogen are overly fertile. They are rarely suitable for recreation, and habitat for desirable aquatic species is limited (eg, Lake Forsyth in Canterbury).
Care should be taken when interpreting these results. Monitored lakes consist of approximately 4 percent of all lakes, and programmes may focus on those that have poor water quality, or are at risk due to land use in their catchment. The lakes included in this analysis, after filtering for continuity, are sparsely and unevenly distributed, with gaps in the Manawatu, Taranaki, Tasman, Marlborough, Otago and West Coast regions.
The accuracy of the data source is of medium quality.
Reference:
Burns, N, Bryers, G, & Bowman, E (2000). Protocols for monitoring trophic levels of New Zealand lakes and reservoirs. Available from www.mfe.govt.nz."
Metadata Constraints
Legal Constraints
Use Limitation
Creative Commons Attribution 3.0 New Zealand by Ministry for the Environment
Access Constraints
Restriction Code
license
Metadata Constraints
Legal Constraints
Use Limitation
Creative Commons Attribution 3.0 New Zealand by Ministry for the Environment
